Accessory drive gear for integrated drive generator

ABSTRACT

An accessory drive gear for use in the integrated drive generator includes a gear body extending between a first end and a second end and having a plurality of gear teeth at a radially outer surface adjacent the first end, and the gear teeth having a gear tooth profile, with roll angles A, B, C, and D, and the roll angle at A being between 17.0 and 18.5°, the roll angle at B being between 20.0 and 21.5°, the roll angle at C being between 29.5 and 31.0°, and the roll angle at D being between 32.5 and 34.0°. In addition, an integrated drive generator is disclosed as is a method of replacing an accessory drive gear in an integrated drive generator.

BACKGROUND OF THE INVENTION

This application relates to an accessory drive gear for use in anintegrated drive generator.

Integrated drive generators are known and often utilized in aircraft. Asknown, a gas turbine engine on the aircraft provides a drive input intoa generator input shaft. The generator typically includes a disconnectshaft that can transmit the input into a gear differential. The geardifferential selectively drives a main generator to provide electricpower for various uses on the aircraft.

It is desirable that the generated power be of a desired constantfrequency. However, the speed from the input shaft will vary duringoperation of the gas turbine engine. This would result in variablefrequency.

Integrated drive generators are provided with speed trimming hydraulicunits. Gears associated with the differential and, in particular, a ringgear portion, provide rotation from the differential back into thetrimming unit. A carrier also rotates another portion of the trimmingunit. The trimming unit is operable to result in the output speed of thedifferential being effectively constant, such that electric power of adesirable frequency is generated.

The generator is mounted between two housing portions and a seal plateis mounted between the two housing portions.

In addition, various accessory systems, such as various pumps, aredriven by the carrier of the differential through an accessory drivegear.

In addition, various accessory systems, such as various pumps, aredriven by an input shaft to a carrier of the differential and through anaccessory drive gear.

The accessory drive gear must successfully provide rotational input to apair of driven gears. There are challenges with regard to the accessorydrive gear.

SUMMARY OF THE INVENTION

An accessory drive gear for use in the integrated drive generatorincludes a gear body extending between a first end and a second end andhaving a plurality of gear teeth at a radially outer surface adjacentthe first end, and the gear teeth having a gear tooth profile, with rollangles A, B, C, and D, and the roll angle at A being between 17.0 and18.5°, the roll angle at B being between 20.0 and 21.5°, the roll angleat C being between 29.5 and 31.0°, and the roll angle at D being between32.5 and 34.0°.

In addition, an integrated drive generator is disclosed as is a methodof replacing an accessory drive gear in an integrated drive generator.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an integrated drive generator.

FIG. 2 shows an accessory gear drivetrain.

FIG. 3A shows an accessory drive gear in accordance with thisdisclosure.

FIG. 3B is a cross-section.

FIG. 4 shows gear teeth on a disclosed accessory drive gear.

DETAILED DESCRIPTION

FIG. 1 shows an integrated drive generator 20. As shown, housingportions 18 and 19 surround the integrated drive generator and a sealplate 17 sits between the housing portions 18 and 19.

A gas turbine engine 22 may drive an input shaft 23 which selectivelydrives a disconnect assembly 26. The disconnect assembly 26, in turn,drives a carrier shaft 28, which drives a carrier in a gear differential30.

As the carrier shaft 28 rotates, planet gears 36 and 38 are caused torotate. Gears 38 have a gear interface 42 with a first ring gear portion40. Gears 36 have a gear interface 48 with a second ring gear portion46.

Ring gear portion 40 has a gear interface 50 with a main generator drivegear 52. When drive gear 52 is driven to rotate, it rotates a rotor 56associated with a stator 58 of the main generator as well as an exciterrotor 60. Electric power is generated for a use 62, as known.

It is desirable that the frequency of the generated electric power be ata desired frequency. This requires the input speed to gear 52 to berelatively constant and at the desired speed. As such, the speed of theinput shaft 23 is added to the speed of the speed trimmer 66 to resultin a constant input speed to gear 52.

A gear 15 that is part of the carrier has a gear interface 16 with agear 13 driving a shaft 14 also within the speed trimmer.

As known, the speed trimmer 66 includes a variable unit 72 and a fixedunit 76. The units 72 and 76 may each be provided with a plurality ofpistons and a swash plate arrangement. If the input speed of the gear 13is too high, the speed of the gear 52 will also be too high, and hence,the speed trimmer 66 acts to lower the speed of the trim gear 46 whichwill drop the speed of gear 52. On the other hand, if the input speed istoo low, the speed trimmer will increase the trim gear speed and thespeed seen by gear 52 will increase.

In essence, the variable unit 72 receives an input through gear 13 thatis proportional to the speed of the input shaft 23. The variable unit 72also receives a control input from a control monitoring the speed of thegenerator rotor 56. The position of the swash plate in the variable unit72 is changed to in turn change the speed and direction of the fixedunit 76. The fixed unit 76 can change the speed, and direction ofrotation of the shaft 70, and this then provides control back throughthe trim ring gear 46 to change the speed reaching the generator. Inthis manner, the speed trimmer 66 results in the frequency generated bythe generator being closer to constant, and at the desired frequency.

A permanent magnet generator 32 rotates with the ring gear 40.

An accessory drive shaft 29 rotates with the carrier shaft 28 and drivesa plurality of accessory gears 31.

The operation of the integrated drive generator 20 is generally as knownin the art. A worker of ordinary skill would recognize that the desiredfrequency and speed at use 62 would dictate a number of designfunctions.

FIG. 2 shows the accessory drive gear 29. The accessory drive gear 29drives a pair of driven gears 99. These driven gears were shownschematically as gear 31 in FIG. 1. One gear 99 drives a second gear 102which, in turn, drives a governor 104. The gear 99 also drives aninversion pump 100. Also, the second gear 99 drives a deaerator throughgear 108, as well as a charge pump 110 and a scavenge pump 112.

Accessory drive gear 29 is illustrated in FIG. 3A. A gear body has gearteeth at an outer periphery 127. As shown, gear teeth 126 extend from aforward end 122 to a rear end 124. A rear end 120 of the overall gear 29is spaced from end 122 by a first distance d₁ or an overall length. Thedistance between the gear teeth ends 122 and 124 is defined as adistance d₂ or a width. An inner diameter of an inner bore 134 is d₃.

As shown, an enlarged channel 136 is formed to be radially outward fromthe nominal inner bore surface of inner bore 134 more adjacent the rearend 120. Oil 130 is delivered into the inner bore of the accessory drivegear 29 and moves outwardly through oil outlet ports 138 in a wall ofthe channel 136 to cool the winding of the permanent magnet generator32. In embodiments, there are two of the ports 138 spaced by 180degrees. A distance to the inner surface at the channel is defined asd₄. In disclosed embodiments, d₁ was 1.071 inches (2.72 cm) and d₂ was0.441 inch (1.12 cm).

In embodiments, d₃ is 1.29995 inches and d₄ is 1.330 inches. In a priorart accessory drive gear, d₁ was 0.8 inch (2.03 cm), d₂ was 0.346 inch(0.88 cm), d₃ was 1.187 inches (3.01 cm).

In embodiments, a ratio of d₁ to d₂ is between 2.35 and 2.5. A ratio ofd₃ to d₄ is between 1.01 and 1.15.

FIG. 3B shows a cross-section of accessory drive gear 29. A keyway 200is shown to secure the gear to a shaft. A distance d₅ is defined from abottom surface of the keyway 200 to an opposed point on nominal innerbore 134. In embodiments, d₅ is 1.38 inches (3.51 cm), with a toleranceof 0.01 inch (0.03 cm).

FIG. 4 shows a gear tooth profile 126. As shown, a pitch diameter PD isdefined. As is known in the gear tooth art, the profile of the geartooth 126 is defined by roll angles at four points A, B, C, D. It shouldbe understood specific roll angles of this disclosed accessory drive arenovel. All that is known in the art is the specific location of thepoints A-D.

In a disclosed embodiment, the roll angle at A is 17.87 degrees, and inembodiments between 17.0 and 18.5°. The roll angle at B is 20.97 degreesand in embodiments, it is between 20.0 and 21.5°. The roll angle at C is30.25 degrees and in embodiments, it is between 29.5 and 31.0°. The rollangle at D is 33.35 degrees and in embodiments, it is between 32.5 and34.0°.

The roll angle A is applied at the form diameter FD. In this portion,the maximum form diameter is 1.75635. The roll angle B is 20% away fromroll angle A, between roll angle A and roll angle D, and the roll angleC is 80% away from roll angle A, between roll angle A and roll angle D.The roll angle D is at the outer diameter of the gear tooth 126.

In embodiments, the diameter to the outer surface of the gear teeth 126is 1.940 inches 4.93 cm). The pitch diameter is 1.85 inches (4.7 cm). Aroot diameter is 1.715 inches (4.36 cm). These are all with a toleranceof 0.1 inch (0.03 cm). There are 37 teeth.

A method of replacing an accessory drive gear includes the steps ofremoving an existing accessory drive gear from an integrated drivegenerator having an input shaft, a gear differential including a carriershaft and the gear differential including a ring gear for driving agenerator. The carrier shaft was connected to drive the existingaccessory drive gear. The existing accessory drive gear drives at leastone driven gear to, in turn, drive at least one pump.

The existing accessory drive gear is replaced with a replacementaccessory drive gear including a gear body extending between a forwardend and a rear end and having a plurality of gear teeth at a radiallyouter surface adjacent the forward end. The gear teeth have a gear toothprofile, with roll angles at A, B, C, and D. The roll angle at A isbetween 17.0 and 18.5°. The roll angle at B is between 20.0 and 21.5°.The roll angle at C is between 29.5 and 31.0°, and the roll angle at Dis between 32.5 and 34.0°.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this invention. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this invention.

1. An accessory drive gear for use in the integrated drive generatorcomprising: a gear body extending between a first end and a second endand having a plurality of gear teeth at a radially outer surfaceadjacent said first end, and said gear teeth having a gear toothprofile, with roll angles A, B, C, and D, and the roll angle at A beingbetween 17.0 and 18.5°, the roll angle at B being between 20.0 and21.5°, the roll angle at C being between 29.5 and 31.0°, and the rollangle at D being between 32.5 and 34.0°.
 2. The accessory drive gear asset forth in claim 1, wherein said gear teeth extend for a width awayfrom said first end and there being an overall axial length of saidaccessory drive gear from said first end to a second end and a ratio ofsaid overall axial length to said width of said gear teeth being between2.35 and 2.5.
 3. The accessory drive gear as set forth in claim 2,wherein said gear body having an inner bore with a nominal inner boresurface extending from said first end toward second end and an enlargedchannel formed from said second end to meet said nominal inner boresurface, and oil outlet ports extending through a wall of said gear bodywithin said channel.
 4. The accessory drive gear as set forth in claim3, wherein a ratio of an inner diameter to said nominal inner boresurface to an inner diameter of said channel is between 1.01 and 1.115.5. The accessory drive gear as set forth in claim 4, wherein a diameterto an outer diameter of 1.94 inches (4.93 cm), a pitch diameter of 1.85inches (4.7 cm), and a root diameter of 1.75 inches (4.45 cm), each witha tolerance of ±0.1 inch (0.25 cm).
 6. The accessory drive gear as setforth in claim 1, wherein said gear body having an inner bore with anominal inner bore surface extending from said first end toward saidsecond end and an enlarged channel formed from said second end to meetsaid nominal inner bore surface, and oil outlet ports extending througha wall of said gear body within said ditch.
 7. An integrated drivegenerator comprising: an input shaft, a gear differential including acarrier shaft to be driven by said input shaft including a ring gearconnected for driving a generator; said carrier shaft also connected todrive an accessory drive gear, said accessory drive gear connected todrive at least one driven gear to, in turn, drive at least one pump; andsaid accessory drive gear including a gear body extending between afirst end and a second end and having a plurality of gear teeth at aradially outer surface adjacent said first end, and said gear teethhaving a gear tooth profile, with roll angles A, B, C, and D, and theroll angle at A being between 17.0 and 18.5°, the roll angle at B beingbetween 20.0 and 21.5°, the roll angle at C being between 29.5 and31.0°, and the roll angle at D being between 32.5 and 34.0°.
 8. Theintegrated drive generator as set forth in claim 7, wherein said gearteeth extend for a width away from said first end and there being anoverall axial length of said accessory drive gear from said first end tosaid second end and a ratio of said overall axial length to said widthof said gear teeth being between 2.35 and 2.5.
 9. The integrated drivegenerator as set forth in claim 8, wherein said gear body having aninner bore with a nominal inner bore surface extending from said firstend toward said second end and an enlarged channel formed from saidsecond end to meet said nominal inner bore surface, and oil outlet portsextending through a wall of said gear body within said channel.
 10. Theintegrated drive generator as set forth in claim 9, wherein a ratio ofan inner diameter to said nominal inner bore surface to an innerdiameter of said channel is between 1.01 and 1.115.
 11. The integrateddrive generator as set forth in claim 10, wherein a diameter to an outerdiameter of 1.94 inches (4.93 cm), a pitch diameter of 1.85 inches (4.7cm), and a root diameter of 1.75 inches (4.45 cm), each with a toleranceof ±0.1 inch (0.25 cm).
 12. The integrated drive generator as set forthin claim 7, wherein said gear body having an inner bore with a nominalinner bore surface extending from said first end toward said second endand an enlarged channel formed from said second end to meet said nominalinner bore surface, and oil outlet ports extending through a wall ofsaid gear body within said channel.
 13. The integrated drive generatoras set forth in claim 7, wherein said at least one pump including aninversion pump.
 14. The integrated drive generator as set forth in claim13, wherein said auxiliary drive gear connected for driving two drivengears, with a first of said driven gears driving said inversion pump anda generator, and a second of said driven gears driving a deaerator. 15.A method of replacing accessory drive gear comprising the steps of:removing an existing accessory drive gear from an integrated drivegenerator having an input shaft, a gear differential including a carriershaft and the gear differential including a ring gear for driving agenerator; said carrier shaft also connected for driving said existingaccessory drive gear, said existing accessory drive gear connected fordriving at least one driven gear to, in turn, drive at least one pump;and replacing the existing accessory drive gear with a replacementaccessory drive gear including a gear body extending between a first endand a second end and having a plurality of gear teeth at a radiallyouter surface adjacent said first end, and said gear teeth having a geartooth profile, with roll angles at A, B, C, and D, and the roll angle atA being between 17.0 and 18.5°, the roll angle at B being between 20.0and 21.5°, the roll angle at C being between 29.5 and 31.0°, and theroll angle at D being between 32.5 and 34.0°.
 16. The method ofreplacing accessory drive gear as set forth in claim 15, wherein saidgear teeth extend for a width away from said first end and there beingan overall axial length of said accessory drive gear from said first endto said second end and a ratio of said overall axial length to saidwidth of said gear teeth being between 2.35 and 2.5.
 17. The method ofreplacing accessory drive gear as set forth in claim 16, wherein saidgear body having an inner bore with a nominal inner bore surfaceextending from said first end toward said second end and an enlargedchannel formed from said second end to meet said nominal surface innerbore, and oil outlet ports extending through a wall of said gear bodywithin said channel.
 18. The method of replacing accessory drive gear asset forth in claim 17, wherein a ratio of an inner diameter to saidnominal inner bore surface to an inner diameter of said channel isbetween 1.01 and 1.115.
 19. The method of replacing accessory drive gearas set forth in claim 19, wherein a diameter to an outer diameter of1.94 inches (4.93 cm), a pitch diameter of 1.85 inches (4.7 cm), and aroot diameter of 1.75 inches (4.45 cm), each with a tolerance of ±0.1inch (0.25 cm).
 20. The method of replacing accessory drive gear as setforth in claim 15, wherein said gear body having an inner bore with anominal inner bore surface extending from said first end toward saidsecond end and an enlarged channel formed from said second end to meetsaid nominal surface inner bore, and oil outlet ports extending througha wall of said gear body within said channel.